FIG. 11 is a schematic explanatory view showing a conventional projector. This projector comprises an illumination optical system 520, a color light separation optical system 530, a relay optical system 540, three liquid crystal panels 550R, 550G and 550B, a cross dichroic prism 560, and a projection optical system 570.
The illumination optical system 520 comprises a light source unit 510, a first and a second lens array 521 and 522, a polarization conversion element 523, and a superimposing lens 524. The first lens array 521 includes a plurality of small lenses for dividing light from the light source 510 into a plurality of light bundles. The second lens array 522 and the superimposing lens 524 form images of each small lens in the first lens array on the liquid crystal panels. Also, the superimposing lens 524 superimposes the light bundles on the liquid crystal panels 550R, 550G and 550B. It should be noted that the polarization direction of the light emitted from the illumination optical system 520 is aligned into one type of direction by the polarization conversion element 523.
Light W emitted from the illumination optical system 520 is separated into the three color lights of red (R), green (G), and blue (B) at the color light separation optical system 530. Each color light R, G and B enters each of the three liquid crystal panels 550R, 550G, 550B through collimating lenses 534, 535, 536 respectively. The blue light B passes through the relay optical system 540 to enter the liquid crystal panel 550B. The liquid crystal panels 550R, 550G and 550B modulate the color lights R, G and B respectively according to given image information. The modulated color lights are combined by the cross dichroic prism 560, and the combined light is projected onto a screen by the projection optical system 570.
The projector comprises a base frame (not illustrated) on which the above optical components are mounted. Each optical component is positioned by means of positioning section such as a concave portion and a convex portion provided in the base frame.
By the way, the optical system and base frame are changed depending on the projector model. For example, the projection optical system and liquid crystal panels are changed depending on the model. The illumination optical system is also changed depending on those changes. Further, the base frame is changed depending on changes to the optical systems in the projector. Namely, a dedicated base frame is conventionally prepared for each model having a different optical system. Because of this, there was the conventional problem that design changes for projectors required time and labor. This problem is not limited to projectors, but is common to other systems having an illumination optical system.